Puelche

The Puelche is a warm easterly wind which has crossed the Andes from Argentina towards Chile. In fact it might cause the Andean foehn of the South American west coast when tapping moisture from the S Atlantic Ocean. The interesting thing about the Puelche and is that it is affected by all of the three important local wind generating factors, which can either amplify it or weaken the Puelche.

Synoptically the Puelche is mainly caused by S Pacific high pressure extending eastwards across the Andes and/or building a ridge to an area of high pressure centered over the S Atlantic. A more short lived and less frequent puelche event may occur when a depression is moving in a NW to SE direction across S Patagonia. However, the Puelche is only known to be a foehn wind in Southern Chile. Further towards the north the easterly winds are often lacking the moisture that would be needed to change their characteristics.

The Puelche blows strongest during nighttime, when being enhanced by the local land breeze and mountain wind system. Consequently it weakens during the day as the local sea breeze and valley wind are acting against it. The corresponding westerly wind is known as virazon.